tinyusb/test/vendor/ceedling/plugins/subprojects/config/defaults.yml

---
#:extension:
#  :subprojects: '.a'

:subprojects:
  :paths: []
#   - :name: subprojectA
#     :source:
#       - ./first/subproject/dir
#       - ./second/subproject/dir
#     :include:
#       - ./first/include/dir
#     :build_root: ./subproject/build/dir
#     :defines:
#       - FIRST_DEFINE

:tools:
  :subprojects_compiler:
    :executable: gcc
    :arguments:
      - -g
      - -I"$": COLLECTION_PATHS_SUBPROJECTS
      - -D$: COLLECTION_DEFINES_SUBPROJECTS
      - -c "${1}"
      - -o "${2}"
  :subprojects_linker:
    :executable: ar
    :arguments:
      - rcs
      - ${2}
      - ${1}

...